1. Technical Field
The invention relates to a liquid transfer system. More particularly, the invention relates to a magnetically controlled liquid transfer system which uses a ferrous actuator and a magnetic air valve to control the directional flow of compressed air passing either through a venturi manifold to create either a vacuum condition or a pressure condition within a pump chamber or flowing directly into the pump chamber allowing for the transfer of liquids from one location to another.
2. Background Information
Liquid transfer systems allow for the transfer of liquids from one location to another without the possibility of contaminating the liquids with lubricants which may be contained within the pump. These liquid transfer systems have been in use for many years and patents can be traced back as far as 1938, as evidenced by U.S. Pat. No. 2,141,427. The theory behind these systems is that compressed air which is passed through a venturi manifold and out an exhaust creates a jet stream. By passing this jet stream directly over an opening in a pump chamber, a vacuum is induced within the pump chamber. The bottom of the chamber includes an inlet passage and an outlet passage each containing a one-way check valve. When the vacuum condition exists within the pump chamber liquid is drawn through the inlet valve and into the pump chamber. When the liquid reaches a certain level within the chamber a valve is shut at the exhaust forcing the air through the opening in the pump chamber and creating a downward pressure on the liquid which forces the liquid out through the outlet valve to another location. This suction-discharge pumping cycle is repeated until the compressed air is discontinued.
In the alternative, the compressed air may flow directly into the pump chamber for forcing the liquid therefrom, which liquid enters the chamber through the force of gravity, such as in a condensation-type of pump.
U.S. Pat. No. 2,141,427 shows a transfer system incorporating a float mechanism to regulate the level of the liquid within the pump chamber. A spring and piston is used to change the directional flow of the compressed air and thus change the pumping cycle from suction to discharge.
One problem with some of the prior art liquid transfer systems is that while corrosive, erosive, or abrasive liquids are drawn into the pump chamber, the level of liquid rises and approaches the opening in the pump chamber. Liquid may splash or be drawn into the jet stream contacting operational elements of the pump or are blown out of the exhaust and into the surrounding environment.
Other difficulties with some prior art liquid transfer systems are with the mechanisms and methods used to measure the level of the liquid and to control the directional flow of air within the pump chamber. U.S. Pat. No. 3,932,065 shows a prior art transfer system which utilizes a pneumatically controlled air valve to change the directional flow of the liquid. The liquid transfer system of the present invention utilizes a magnetically controlled diverter valve to perform the same task.
U.S. Pat. No. 5,007,803 shows a liquid transfer system which uses either two opto-electronic sensors or a pneumatic timing device to signal the opening and closing of a pinch valve. The pinch valve is placed at the exhaust and includes an internal flexible sleeve. When the pinch valve is in an open position air flows through the sleeve and out the exhaust. When in a closed position, pressure is applied against the flexible sleeve causing the sleeve to pinch inwardly closing off the airflow through the exhaust. When the valve is closed the air is directed into the chamber forcing the liquid through the outlet valve. Although the system of this patent is presumably adequate for the purpose for which it was intended, the present invention avoids the drawbacks of this prior art liquid transfer system.
One drawback of this prior art liquid transfer system is the use of the pinch valve. The pinch valve requires 30 psi to close the flexible sleeve and redirect the compressed air into the pump chamber. Therefore, if the pump is being operated at, for example 50 psi during both the pressure and suction cycles, an additional 30 psi or a total of 80 psi would be required to close the pinch valve. This reservation of the total available pumping pressure decreases the efficiency and speed of the pump.
Another drawback of the system of U.S. Pat. No. 5,007,803 is that it uses timers to control the pump cycles. These timers have defined ranges which restrict the period of the pumping cycles. Liquids with a high viscosity have a slower flow rate than liquids with a lower viscosity. Thus during the suction cycle these high viscosity liquids take a longer period of time to be drawn into the pump chamber and the timer may time-out and switch cycles before the liquid sufficiently fills the pump chamber. During the discharge cycle if a large head pressure exists, the timers may time-out before the liquid is completely discharged from the pump chamber. Thus in both the suction and the discharge cycles the maximum amount of fluid may not be transferred from and to the desired locations, and time that could be spent pumping liquids is spent switching cycles.
Another type of liquid transfer system is referred to as a condensation pump, in which liquid enters a pump chamber under the influence of gravity, after which it is subsequently discharged by various control means, including float valves. However, the control systems of these prior art condensation pumps do not provide the advantages of the magnetically controlled system of the present invention.
Thus, the need exists for a liquid transfer system which allows the maximum amount of liquid to be transferred per pumping cycle, which requires minimal air pressure to switch between cycle positions, which allows a greater amount of the air pressure to be used for pumping, and which provides a device within the pump chamber to restrict liquids from being splashed or sucked up through the pump chamber opening possibly coming into contact with operational pump elements or being blown into the surrounding environment.